How to add 3rd party VST Instrument?


I have just purchased Cubase elements 7. Earlier I collected few 3 rd party VST Instruments (synths) with dll extension. How can I use them?
(I checked all the paths in device/VSP plugin menu however none of them has an extension of dll and if I follow the path there and save the VST instrument e.g. where Halion is found I can not see among the selectable items)


Sorry meanwhile realised that dll for win and I have mac…apology